With the growing concern over global climate change as well as oil supplies, there has been a recent trend to develop various hybrid systems for motor vehicles. While numerous hybrid systems have been proposed, the systems typically require significant modifications to the drive trains of the vehicles. These modifications make it difficult to retrofit the systems to existing vehicles. Moreover, some of these systems have a tendency to cause significant power loss, which in turn hurts the fuel economy for the vehicle. Thus, there is a need for improvement in this field.
One of the areas for improvement is in the construction and arrangement of the hydraulic system. Hybrid vehicles, and in particular the hybrid module associated with such a vehicle, have various lubrication and cooling needs which depend on engine conditions and operational modes. In order to address these needs, oil is delivered by at least one hydraulic pump. The operation of each hydraulic pump is controlled, based in part on the lubrication and cooling needs and based in part on the prioritizing when one or more hydraulic pump is included as part of the hydraulic system of the hybrid vehicle. The prioritizing between hydraulic pumps is based in part on the needs and based in part on the operational state or mode of the hybrid vehicle.
Another area for improvement within the overall hydraulics of the hybrid vehicle is in the management of the oil level within the torque converter housing. An electric oil pump is used as a scavenge pump for the oil sump of the torque converter housing. The scavenge pump is part of a “dry” sump oil lubrication system which requires that the collecting oil sump pan be kept relatively dry compared to what is generally understood as a wet sump oil lubrication system.
One of the concerns relating to dry sump configurations and systems is oil aeration which occurs when too little oil is present in the oil sump. This is the result of excessive scavenging. Another concern is oil flooding which occurs when too much oil is present in the oil sump. This is the result of insufficient or inadequate scavenging. Related concerns are the monetary and energy costs associated with maintaining an oil level sensor in the sump. The control system described herein addresses the first two concerns by monitoring the scavenge pump and adjusting the scavenge pump performance to try and maintain a desired oil level in the sump.